How to distinguish calling a c library function from making a system call?-CodePudding

There is the C library function pipe(3) and the kernel (system call) pipe(2). Both have the same signature and should be used like this (same include header):

#include <unistd.h>
int fds[2];
pipe(fds);

Will this code call pipe(3) or pipe(2)? How can I decide whether I want to use libc or a system call? If pipe(3) and pipe(2) are the same, how do I know that?

CodePudding user response：

I think you're making a distinction where there isn't one. Your code will call the pipe library function, which is just a wrapper around the pipe system call. It's not an either/or. The section 3 manual page is from the POSIX programmer's manual, and the section 2 manual page is Linux-specific.

CodePudding user response：

Will this code call pipe(3) or pipe(2)?

It will call pipe(3).

There is no way to call the system call directly from C, you either

have to call libc wrapper for such system call (if one is provided), or
use syscall(2) to "stuff" the right arguments into the right registers before executing architecture-appropriate system call instruction, or
provide your own assembly wrapper which will do the same, or
use inline __asm__ to do the same.